remove getsxts for better function readb

Decoding input is read faster now.
With this, all options have been tuned to a reasonable degree.

main.c

@@ -53,7 +53,7 @@ main(int argc, char *argv[])
             exit(EXIT_FAILURE);
         }
         if (dec) {
-            while ((n = getsxts((in) ? in : stdin, sbuf))) {
+            while ((n = readb((in) ? in : stdin, sbuf, SXTETBUF))) {
                 n = decode(sbuf, n, obuf, url);
                 fwrite(obuf, sizeof(*obuf), n, (out) ? out : stdout);
             }